Silicon nitride sintered body

Abstract

A silicon nitride sintered body includes silicon nitride as a principal component, silicon carbide dispersed therein and at least one of boron and boron compounds in an amount of from 0.005 to 0.5% by weight in terms of the weight of boron with respect to the total weight of the sintered body. The addition of boron or boron compounds improves the high-temperature characteristics such as creep resistance of the sintered body.

What is claimed is: 
     
       1. A silicon nitride sintered body comprising silicon nitride as a principal component, silicon carbide dispersed in the sintered body and at least one member selected from the group consisting of boron and boron compounds in an amount of from 0.005 to 0.5% by weight in terms of the weight of boron with respect to the total weight of said sintered body. 
     
     
       2. A silicon nitride sintered body as claimed in claim 1, wherein said at least one member is included in an amount of from 0.05% to 0.10% by weight in terms of the weight of boron. 
     
     
       3. A silicon nitride sintered body as claimed in claim 1, wherein said boron compound is at least one selected from the group consisting of a boron oxide, a boron carbide, a boron chloride, and a boron fluoride. 
     
     
       4. A silicon nitride sintered body as claimed in claim 3, wherein said boron oxide is B 2  O 3 . 
     
     
       5. A silicon nitride sintered body as claimed in claim 1, wherein said silicon nitride has an average crystal grain diameter of 5.0 mm or less in the sintered body. 
     
     
       6. A silicon nitride sintered body as claimed in claim 1, wherein said silicon carbide has an average crystal grain diameter of 0.5 mm or less in the sintered body. 
     
     
       7. A silicon nitride sintered body as claimed in claim 1, wherein the content ratio by weight of said silicon nitride to said silicon carbide ranges from 95/5 to 1/1. 
     
     
       8. A silicon nitride sintered body as claimed in claim 1, further comprising a sintering aid. 
     
     
       9. A silicon nitride sintered body as claimed in claim 8, wherein said sintering aid is Y 2  O 3 .